Electrical circuitry, such as power amplifiers, often add undesired distortion to an input signal, creating an output signal comprised of a distortion component and an input signal component. R. E. Myer, U.S. Pat. No. 4,580,105, issued Apr. 1, 1986, discloses a prior art technique in FIG. 1, for reducing the distortion component created by a power amplifier 14. This technique involves taking a portion of the output signal and combining it with an input signal which has been adjusted in phase and amplitude. This signal combination, isolates the distortion component of the output signal. The isolated distortion component is adjusted in phase and gain, and then added back to the output signal at a coupler 10, to eliminate the distortion component and obtain the desired input signal component. One of the disadvantages of the prior art technique disclosed in Myer, U.S. Pat. No. 4,580,105, is that a significant amount of power of the output signal is lost when the isolated distortion component signal is added in at the coupler 10. This loss of power can be offset by increasing the size of the power amplifier 14, however that is expensive.
R. E. Myer, U.S. Pat. No. 4,879,519, issued Nov. 7, 1989, discloses another technique for reducing distortion produced by a power amplifier. In that patent, a pre-distortion signal from a combiner 115 is applied to the inputs of amplifiers 135-1 through 135-N. The pre-distortion signal is opposite in phase and is designed to cancel the distortion component that is subsequently introduced by the amplifiers 135-1 through 135-N. (FIG. 1, col. 3, ln. 55-col. 4, ln. 8)